AC Compressor clutch won't engage

[michaelbrainardatwor]

I know I know...this has been asked a million times...maybe someone can point me in the right direction

1990 F350 7.3L

AC worked fine all summer until this fall....

I have not determined if there is current going to the compressor.

Compressor turns fine by hand

Does the cycling switch on the dryer activate the compressor clutch? Could this be bad?

Any proceedures to start chasing this down? Thanks

[ford390gashog]

i would make sure you have power to the clutch first.

[michaelbrainardatwor]

Originally Posted by ford390gashog

i would make sure you have power to the clutch first.

There are two wires connecting to the compressor....is one hot and one ground? Does the engine have to be running for current?

[lsrx101]

Originally Posted by michaelbrainardatwor

I know I know...this has been asked a million times...maybe someone can point me in the right direction

1990 F350 7.3L

AC worked fine all summer until this fall....

I have not determined if there is current going to the compressor.

Compressor turns fine by hand

Does the cycling switch on the dryer activate the compressor clutch? Could this be bad?

Any proceedures to start chasing this down? Thanks

The first thing to do is check the system static pressure. If it's below about 45 psi, then the system charge is low and the cycling switch won't allow the compressor to run.
If the static pressure is above 45 psi, there's likely an electrical issue. Also, turn on the AC and tap the clutch face with a hammer handle or similar tool. If the clutch engages, the clutch gap is too wide.
That should get you started.

[projectSHO89]

If it's extremely cold, the system will register a low pressure anyway. Usually below 40F will keep the system from activating..

Steve